Gallons to Liters Converter

Gallons (gal)

Common sizes

Gallons	L (US gal)	L (UK gal)
½ gal (milk carton)	1.8927	2.273
1 gal (milk jug)	3.7854	4.5461
2 gal	7.5708	9.0922
5 gal (bucket, water jug)	18.9271	22.7305
10 gal (aquarium)	37.8541	45.4609
15 gal (car fuel tank)	56.7812	68.1914
20 gal	75.7082	90.9218
40 gal (water heater)	151.4165	181.8436
55 gal (oil drum)	208.1976	250.035
100 gal	378.5412	454.609

1 US gallon = 3.785411784 L exactly. 1 UK gallon = 4.54609 L exactly.

Type gallons, get liters. The answer updates as you type and gives you two numbers, because a gallon isn't one size: a US gallon is 3.785411784 L and a UK (imperial) gallon is 4.54609 L, about 20% more. US gallons lead; the imperial answer sits right under it. Type "UK" or "imperial" after the number and that answer leads instead. Both use the exact legal definitions, not a rounded 3.79. Use it to read an American recipe, water heater, or aquarium spec in liters, work out how much a 5-gallon bucket of paint really holds, compare fuel prices across a border, or check a British boat or caravan manual without guessing which gallon it means.

Built by Bob QA by Ben Shipped September 15, 2026

How to use

1
Type the volume in gallons. Decimals (2.5), fractions (1/2, 1 1/2, 1½), grouped thousands (1,000), and a trailing gal or gallons all work.
2
Read liters in the result card. The big number assumes US gallons; the line under it gives the UK (imperial) gallon answer.
3
If your gallons are British, add UK or imperial (5 UK gal) and the imperial answer moves to the top.
4
Tap Copy to grab just the liters, or Copy formula to grab the whole calculation. The table below lists common sizes, from a half-gallon carton to a 100-gallon tank.

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Frequently asked questions

How many liters are in a gallon?

A US gallon is exactly 3.785411784 liters — call it 3.79. A UK imperial gallon is exactly 4.54609 liters — call it 4.55. To convert, multiply gallons by the one that matches where the number came from.

Why are there two different gallons?

The US kept the old Queen Anne wine gallon of 231 cubic inches, which works out to 3.785411784 L. Britain replaced its gallons in 1824 with one new gallon, the volume of 10 pounds of water, now fixed at 4.54609 L. So the same "10 gallons" is 37.85 L in Texas and 45.46 L in London. Canada, Ireland, and some Caribbean countries used the imperial gallon before going metric, so older labels there mean imperial too.

How do I know which gallon a label means?

Go by where the number came from. US recipes, American mpg figures, US water heaters, paint, and milk are all US gallons. British mpg, UK boat and caravan manuals, and older Canadian or Irish sources are imperial. If you still can't tell, look at the price or fuel economy: UK mpg figures look about 20% better than US ones for the same car, because their gallon is bigger.

How many liters is a 5-gallon bucket?

18.93 liters for a standard US 5-gallon bucket or water-cooler jug. Water jugs are often sold as 18.9 L or rounded to 19 L for that reason. Five imperial gallons would be 22.73 L, but 5-gallon buckets are almost always the US size.

What's a quick way to convert gallons to liters in my head?

For US gallons, multiply by 4 and take off 5%. 10 gal → 40 → about 38 L (exact: 37.85). Multiplying by 4 alone runs about 6% high, which is fine for a rough idea. For UK gallons, multiply by 4.5: 10 imperial gallons is 45 L (exact: 45.46).

How many liters is a 40- or 50-gallon water heater?

A 40-gallon US water heater holds 151.4 L, and a 50-gallon one holds 189.3 L. Tank sizes on the label are nominal, so the water a tank actually holds can run a few percent under that.

How precise is the answer?

The conversion uses the exact defined values, so the only rounding is for display: four decimals once you're at a liter or more, six below that (0.1 gal shows as 0.378541 L). Very large volumes show as whole liters with commas. Copy formula gives you the full calculation if you need to show your work.

Is what I type saved or sent anywhere?

No. The conversion runs in your browser. Nothing is sent to a server or stored, and closing the tab clears it.

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